A dye precursor which forms a dye by heating is disclosed in WO 90/00978, and a dye precursor represented by the following formula is disclosed as one example: ##STR2##
wherein X represents --NR'R" (wherein R' and R" each is selected from a hydrogen atom and an alkyl group having from 1 to 6 carbon atoms); Y' represents a hydrogen atom, an alkyl group or a substituted alkyl group; and Z and Z' each represents a protective group capable of being removed by heating or a dissociative group.
As examples of a dissociative group on a nitrogen atom or a protective group capable of being removed by heating on a nitrogen atom, an alkylsulfonyl group, an arylsulfonyl group and the groups represented by the following formulae (a) and (b): ##STR3##
wherein R.sup.A1 represents an alkyl group generally having from 1 to 6 carbon atoms, a halomethyl group such as a methyl group substituted with 1, 2 or 3 halo groups (e.g., chloro or bromo), or a substituted or unsubstituted aryl group (generally a phenyl group); ##STR4##
wherein R.sup.A2 and R.sup.A3 each represents a hydrogen atom, an alkyl group or an aryl group (generally a phenyl group); R.sup.A4 represents a hydrogen atom, an alkyl group, an aryl group (generally a phenyl group), or EW; and EW represents an electron attractive group.
However, the dye precursor represented by the above formula having a dissociative group or a protective group represented by Z cannot satisfy the conditions that the heat stability of the dye precursor under a neutral or basic condition should be sufficiently high and the color-forming capability under an acidic condition should be sufficiently high.
Dye precursors which form dyes by oxidizing agents such as silver salts are known and disclosed in WO 94/22052. As these dye precursors form dyes by an oxidation reaction, coupler components other than 4-equivalent couplers cannot be used. Further, these dye precursors did not substantially form dyes by the action of an acid.
That is, dye precursors which substantially do not form a dye by heating the dye precursor alone or by an oxidation reaction but rapidly form a dye by the action of an acid have not been known yet.
However, a photosensitive material containing a dye precursor represented by the above-described formula is not known.
Photosensitive materials containing dye precursors are disclosed in WO 94/22052. As these dye precursors form dyes by an oxidation reaction, coupler components other than 4-equivalent couplers cannot be used. Further, these techniques require to use an oxidizing agent such as a silver salt which is not desirable for a printing material for digital image information output.
That is, photosensitive materials containing dye precursors which do not necessitate oxidizing agents such as silver salts for color-forming have not been known yet.
Dye precursors which form azomethine dyes are disclosed in WO 90/00978 and WO 94/22052. Specific examples of coupler residues for use in the dye precursors disclosed in these publications are a pyrazolone type coupler, a phenol type coupler and a naphthol type coupler. However, magenta and cyan dyes formed from the dye precursors containing these coupler residues were inferior in absorption coefficient and absorption wavelength.